tolerance for acceptable accuracy

[wmitty]

Does a bore riding design's nose have to be land diameter or larger (interference fit) for the boolit to be accurate? I'm using an RCBS .30 - 180 - SP for .30 - 06 and .308 loads and wondered if it would work in a Marlin 336 in .30-30 with it's .304" land dia. ( the nose of the RCBS boolit runs .3015"). I'm in on the group buy for the Lee 6 cavity in the 31141 cavity design. Doe's the nose on this bullet normally mike as small as the RCBS ?

[Pawpaw]

I just now miked several of Wayne Doudna's 311041 bullets just ahead of the driving band. They all went 0.302". I'm on that group buy also, and looking forward to that mold.

[cbrick]

That RCBS mould is a new one for me also (bought it last summer and just got around to casting with it). I checked the nose diameter (cast with WW) and it's .300". This does engrave in the rifling of my TCR 308 but pretty shallow.

I have bought my last RCBS mould. Another new RCBS (last month) I got in 140 gr 6.5mm is horrible. I have invested about a day and a half tweeking and adjusting trying to get it to cast something that at least looks like it should shoot. .010" out of round (the small side is .260") and the cavities look like they were cut with a chisel instead of a cherrie. There is a really deep air vent line across the tip of the bullet nose and it leaves a 1/16" lump on the nose. Was going to send it back but I looked at about a dozen new RCBS moulds in a reloading store and the one I have didn't look to bad compared to some of the others. If that's what they are building now, why send it back and get back something no better than what I have. It's a $50.00 paper weight.

Rick

[NVcurmudgeon]

cbrick, before you give up on RCBS, phone them (you can probably get an 800 no. from their web site.) They have always been way beyond reasonable to me,
even to giving me a free press when I wasn't even complaining, and they did not know for sure that I even owned one of their presses. As others have posted here, if you contact them by phone and get the name of a real human being, you maybe can get them to look at a replacement mould before they sent it out to you. My experience with RCBS is a little dated, as I haven't gotten any unexpected free stuff from them for a year and a half. The latest round of mergers and aquisitions may have changed everything. Good luck.

[Buckshot]

............I like to see definate, positive engraving on my bore riders, and not just mere rub marks. I've proven to myself enough times for me to say that if the bore rider doesn't even touch, then you're in trouble so far as accuracy goes.

..................Buckshot

[cbrick]

NVcurmudgeon,

The following is a cut & paste from an article in Jan 02. This could well explain a lot. What a shame that the mainstay of handloading for decades has taken to turning out trash.

(Federal, Speer, CCI, Weaver, Simmons, Redfield, Outers, Ram-Line), which employs 1700 people, has been sold to Alliant Techsystems (ATK), maker of Alliant Reloading powders and a broad array of other munitions related products. ATK is a multi billion dollar company employing 11,400 people that primarily makes ICBM engines, small rocket and missile motors, military small caliber ammunition, powders for large caliber military artillery, etc.

Buckshot,

I agree. If the nose can wiggle around it will. A bullet that doesn't come out straight goes wherever it pleases . . . and that's usually not where it pleases you.

Rick

[Newtire]

cbrick,
I have several RCBS moulds & they do seem to be on the "small?" side. They say in their little cast bullet book about being closer to bore size means less resizing & better accuracy according to them. My solution for my 165 silhouette bullet was to just buy another rifle that fits it! I have the same trouble with a 311291 Lyman. Undersized on the nose & don't shoot worth a crap yet it's the favorite one of most guys on this board. So now I have an 06 set of rifles & a 30-30 set of rifles. One fat bore & one skinny. There ya go.

[cbrick]

Newtire,

I have about 35 moulds and nearly half of them are RCBS. The worst thing I can say about them is that they are great moulds and some great bullet designs. That is until the last two. I have bought a mould at a gun show and then bought a gun in that caliber so I could shoot the bullet but . . . I'll be damned if I will buy a new firearm to attempt to cure a crappy mould. Seems far more sensible (and cheaper) to get a new mould from a quality mould maker. What RCBS is now turning out as a sorry excuse for bullet moulds has me seriously re-considering buying anything that says RCBS on it if it was made since ATK has owned RCBS.

Once again, what a shame that the mainstay of quality handloading tools for decades has now taken to turning out trash. Burn me once, shame on you (RCBS), burn me twice, shame on me. I have been burned twice in a row, I'll not give RCBS another $50.00 to get me a third time. [smilie=b:

Rick

[Buckshot]

...............Cbrick maybe you just beat the odds and got a couple bad ones? I have 4-5 RCBS moulds and only one was bad. Many years ago I bought a RCBS 7mm-168 and it cast oval boolits. It appears to me that the blocks weren't fully closed when the cavity was cut.

I sent it back to RCBS and got a brand new one. It was exactly the same as the one I'd sent back! I boxed it up with a couple boollits I'd cast in it and sent it back. I got another one back with a couple slugs THEY'D cast, and it was beautiful. I guess there may have been a run of bad 7mm-168's?

So far as recent RCBS moulds, I'd hate to think the guys in the mould department these days either just don't care or are operating under a 'new deal'.

..................Buckshot

[JohnH]

I wonder just how a mold maker (RCBS, Lyman, Saeco, Lee, etc) goes about even choosing a diameter for a 30 cal bore riding design. I've seen barrels from .300 to .307 on the bore, and I've bought molds that were as small as .296 and as large as .303

What I've seen from undersize bore riders is that they will shoot pretty good, sometimes even better than good so long as velocity is under 1300 fps. Get above that and groups go to patterns at best.

[joeb33050]

Does a bore riding design's nose have to be land diameter or larger (interference fit) for the boolit to be accurate? I'm using an RCBS .30 - 180 - SP for .30 - 06 and .308 loads and wondered if it would work in a Marlin 336 in .30-30 with it's .304" land dia. ( the nose of the RCBS boolit runs .3015"). I'm in on the group buy for the Lee 6 cavity in the 31141 cavity design. Doe's the nose on this bullet normally mike as small as the RCBS ?

I find that a small diameter change makes a big difference in the force required to push a bullet into the barrel, and a big change on what the engraving looks like.
I'm thinking about the relationship between hardness of the alloy, bore/groove diameter, and force required to put the cartridge in the chamber.
At some point, as most of us know, a cartridge ends up with the bullet inside the case when we try to chamber it.
So.
For a given barrel size, say .300" X .308", and say WW bullets, and say 311299 for bullet shape, what is the force required to seat bullets of
.300"
.301"
.302"
.303"
.304"
nose diameters?
Some precise bump-up dies would be needed, and a force-measuring device. Maybe a scale. I think I know a guy who can make the dies.
Also, rifling type will vary things, 2 groove vs. microgroove etc.
Also, even with CB's only, the chamber end of the rifling wears a lot in a few hundred rounds, see how max. OAL increases-specially in Stainless Steel (Savage) barrels.
I think that we need bigger noses (on bullets) than we use.
joe b.

[Oldfeller]

Example of your point would be a recent group buy bullet, a loverin. The nose on mine came in at .2995"-.3000" diameter on the nose and the first two driver bands. This is too small to touch the rifling on a Savage rifle, but may mark very well in a Swiss K-31 with its taller rifling (any other 30 cals with noticably taller rifling out there?)

Fitting a micro-groove Marlin, forget it -- way way too small. What is ironic is that the folks made sure the main driver bands were really really large, but the nose is stone undersized to about half the uses that are out there in reality land.

Now, was this a design issue or a LEE issue? I really don't know and probably never will know, not that it really matters anyway as LEE has refused to fix or to recut all the molds recently sent back for corrections even when sent with a drawing. All LEE does is play games with other casting alloys, pressure cast themselves a sightly larger slug out of the "defective" mold and ship it back to you saying it is not defective.

The nose of the bullet has to fit the exit crown of your gun and more importantly your throat area for good loading. Your throat area is significantly bigger than your crown after your gun has been fired a few thousand rounds.

I would suggest the only real solution to this issue is to learn how to selectively lap a mold to fit your individual rifle and its current throat condition. You can lap it out bigger as your rifle's throat grows over the years.

Or buy a fitted custom designed and accurately cut mold from Dan at Mountain Mold. LEE isn't going to do it for you with their .004" production variation in a mold run, not unless you intentionally stick with sizing die controlled Loverin designs that have no reduced diameter nose bands for LEE to undersize or oversize for you.

Oldfeller

[felix]

Kelly, may I dream a little? Measure the cavities in the mold with an incremental light firing mechanism, decipher the existing design parameters by computer to normalize each parameter to maximum cut, and then permit larger dimensions as an override. Send the specs to a good cutting machine to do the work making all cavities exactly the same. ... felix

[Oldfeller]

Felix, it is likely a good bit easier to take the undersized molds that LEE provides us and simply treat them as raw material -- and lap them out to properly fit YOUR gun.

LEE can't even keep the six cavities in a row consistent for size for any one given critical feature, so you will have to lap them anyway to get them to be the same size and so the bullets will drop out of the mold easily on opening.

So why not just plan on fixing your critical to fit features during this same lapping process?

[Buckshot]

.................joe33050, engraving force is going to be different for a 4 groove Springfield/Mauser type barrel then it will be for a 5 land/groove equal width barrel or the Swede/Turk Mauser 4 equal width land/groove barrels, to say nothing of 2 groove barrels.

http://www.fototime.com/BA242B461D7EC7F/standard.jpg
As a rule (as above) I tumble lube my bore riders before lube-sizing. Sure makes the engraving easier.

http://www.fototime.com/982F406A87D7DAC/standard.jpg
This is an 8mm slug intended for military rifles. The noses had been soot blackened to better show the engraving. The OAL of the one on the left is about max for feeding, as it's just coming up on max mag length. Works out as it places the GC right at the neck-shoulder.

The short seated one catches the .318" nose and the longer gets that plus butts the .320" band into the lands. Surprisingly enough all my Turks require sizing at .323". Sized to .325" and the slugs get all scratched up in the throat and end of the chamber. Guess I should make a .324" sizer and see what that does?

....................Buckshot

[Oldfeller]

As to an interference number that equates to "good engraving", 0.001" larger will mark somewhat, 0.003" or more oversize will tend to have hard pull on extraction. And this is measured only at the worn loading throat location, that mythical wear zone that is constantly getting slightly bigger as you shoot.

Let's talk practicality here for a minute. Lee only "claims" .001 roundness and generally hits at no more than .0015"-.0020" TIR across a set of six cavities for a pure roundness measurement. (most of this is alignment pin shift effects during casting)

Lee only claims .003" for diameter control and generally hits .001-.002" undersized with a true range spread of .004" top to bottom on all features within a mold run.

And we are hoping for a nose engraving fit zone of .001" to .002" oversized to our particular gun's throat with our roundness included in that number ????

(and some folks say bullet casters are a bit demanding on a mold maker)

Now here is a real puzzler -- LEE molds also change with time as the knurling breaks in and begins to flatten. I have seen molds with the knurling half gone with extended use. That is thousands and thousands in size/roundness change.

So, if you are planning to use LEE molds accurately, you need to learn how to embedded grit lap your mold features to get what you really want out of them.

Or, plan to only buy iron or steel molds that really fit your needs (then learn how to keep that old debble rust off of them).



============= iron or steel molds that fit YOUR needs? ============


oh well


Accepting the fact you have to learn how to precision lap mold cavities has a side benefit -- you can actually get your molds to drop free on opening.

(even those Loverin types with all them clingy little grooves)